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Chemoselective polymerization control: from mixed-monomer feedstock to copolymers.

Romain DC, Williams CK - Angew. Chem. Int. Ed. Engl. (2014)

Bottom Line: A novel chemoselective polymerization control yields predictable (co)polymer compositions from a mixture of monomers.Using a dizinc catalyst and a mixture of caprolactone, cyclohexene oxide, and carbon dioxide enables the selective preparation of either polyesters or polycarbonates or copoly(ester-carbonates).The selectivity depends on the nature of the zinc-oxygen functionality at the growing polymer chain end, and can be controlled by the addition of exogeneous switch reagents.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Imperial College London, London SW7 2AZ (UK).

No MeSH data available.


Related in: MedlinePlus

Chemoselective polymerization control. a) 1/CHO/CL=1:900:100, 80 °C, 16 h. Gases (CO2 or N2) are added to 1 bar total pressure.
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fig02: Chemoselective polymerization control. a) 1/CHO/CL=1:900:100, 80 °C, 16 h. Gases (CO2 or N2) are added to 1 bar total pressure.

Mentions: Dizinc complex 1 is an efficient ROCOP catalyst, using cyclohexene oxide (CHO) and CO2.141 operates under CO2 pressures as low as 1 bar and is highly selective, producing poly(cyclohexene carbonate) (PCHC) with a high fidelity of carbonate repeat units (>99 %). Given the strong precedent for zinc catalysts in lactone ROP,4c1 was tested for the ROP of caprolactone (CL). However, 1 was completely inactive, even under forcing conditions (80 °C, neat CL, with/without alcohol; Table 1; see also Table S1 in the Supporting Information). This appears to be a thermodynamic limitation, as even reaction for extended periods (16 h, >48 half-lives; see below) failed to yield polycaprolactone (PCL). Catalyst deactivation is ruled out, as 1 can be switched on for ROP by addition of 10 mol % (vs. CL) of an epoxide (Table 1, entry 2). Thus, CL ROP using 1 with 10 % added epoxide (CHO) at 80 °C proceeded to complete conversion (>99 %) within 2 h, yielding only PCL (Figure 2, RHS). The polymerization was well controlled; the PCL Mn (21 000 g mol−1, PDI: 1.4) was in excellent agreement with that predicted Mncalc=22 000 g mol−1). The epoxide switch reagent can be added either in low quantities (10 %) or in excess, for example, as the polymerization solvent (Table 1, runs 3–6).Where CHO is the solvent (at >9×conc. of CL), the PCL shows a reduced Mn owing to chain-transfer reactions with residual water/cyclohexane diol (0.1 mol % vs. CHO); equivalent reactions are common to catalysts in this field.14c, 15


Chemoselective polymerization control: from mixed-monomer feedstock to copolymers.

Romain DC, Williams CK - Angew. Chem. Int. Ed. Engl. (2014)

Chemoselective polymerization control. a) 1/CHO/CL=1:900:100, 80 °C, 16 h. Gases (CO2 or N2) are added to 1 bar total pressure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232277&req=5

fig02: Chemoselective polymerization control. a) 1/CHO/CL=1:900:100, 80 °C, 16 h. Gases (CO2 or N2) are added to 1 bar total pressure.
Mentions: Dizinc complex 1 is an efficient ROCOP catalyst, using cyclohexene oxide (CHO) and CO2.141 operates under CO2 pressures as low as 1 bar and is highly selective, producing poly(cyclohexene carbonate) (PCHC) with a high fidelity of carbonate repeat units (>99 %). Given the strong precedent for zinc catalysts in lactone ROP,4c1 was tested for the ROP of caprolactone (CL). However, 1 was completely inactive, even under forcing conditions (80 °C, neat CL, with/without alcohol; Table 1; see also Table S1 in the Supporting Information). This appears to be a thermodynamic limitation, as even reaction for extended periods (16 h, >48 half-lives; see below) failed to yield polycaprolactone (PCL). Catalyst deactivation is ruled out, as 1 can be switched on for ROP by addition of 10 mol % (vs. CL) of an epoxide (Table 1, entry 2). Thus, CL ROP using 1 with 10 % added epoxide (CHO) at 80 °C proceeded to complete conversion (>99 %) within 2 h, yielding only PCL (Figure 2, RHS). The polymerization was well controlled; the PCL Mn (21 000 g mol−1, PDI: 1.4) was in excellent agreement with that predicted Mncalc=22 000 g mol−1). The epoxide switch reagent can be added either in low quantities (10 %) or in excess, for example, as the polymerization solvent (Table 1, runs 3–6).Where CHO is the solvent (at >9×conc. of CL), the PCL shows a reduced Mn owing to chain-transfer reactions with residual water/cyclohexane diol (0.1 mol % vs. CHO); equivalent reactions are common to catalysts in this field.14c, 15

Bottom Line: A novel chemoselective polymerization control yields predictable (co)polymer compositions from a mixture of monomers.Using a dizinc catalyst and a mixture of caprolactone, cyclohexene oxide, and carbon dioxide enables the selective preparation of either polyesters or polycarbonates or copoly(ester-carbonates).The selectivity depends on the nature of the zinc-oxygen functionality at the growing polymer chain end, and can be controlled by the addition of exogeneous switch reagents.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Imperial College London, London SW7 2AZ (UK).

No MeSH data available.


Related in: MedlinePlus